The present invention relates to friction disc clutch assemblies, and more particularly to an improvement of a clutch disc assembly to render quick declutching operation of the clutch assembly.
Usually, friction clutches of the disc type include a clutch disc assembly which is axially slidable on a driven shaft. The clutch disc assembly is interposed between a flywheel and a pressure plate and fitted with friction facings adapted for engagement with both the flywheel and the pressure plate to transmit the rotation torque of the drive shaft to the driven shaft. In the declutching operation, such a negative means as vibration of the engine is adapted to disengage the clutch disc from the flywheel. However, if there is insufficient sliding action of the clutch disc along the drive shaft, the clutch disc cannot disengage quickly from the flywheel, and this causes undesired friction within the clutch assembly.
As shown in FIG. 1, to avoid the above drawbacks, a clutch disc assembly 10 has been recently proposed which is provided with a pair of annular friction facings 11 and 12 in the form of a truncated-conical shape.
In the disengaged state, each of the friction facings 11, 12 is contiguous to the side-face fo flywheel 20 at its inner periphery and is spaced from the flywheel 20 at its outer periphery. In the engaged stage, the friction facings 11, 12 are gripped and flattened between the flywheel 20 and the pressure plate 30 to store self-return or reaction forces therein. Upon declutching, the reaction forces return the friction facings 11, 12 to their original shapes as shown in FIG. 1 to cause quick disengagement of the friction clutch. In the practical use of such friction facings 11, 12, the declutching operation will be disturbed by slight contact of the facing 11 with the side-face of flywheel 20, and the outer periphery of facing 12 will be distorted by heat of friction.
To avoid the above-noted disadvantages, it is desirable that annular members 11a, 12a of low frictional coefficient material are firmly attached to the inner periphery of facing 11 and the outer periphery of facing 12. This serves to decrease drag torque transmitted to the clutch disc assembly, but the attached annular members are apt to be detached from the respective facings due to heavy torque from flywheel 20 and heat of friction.